Update 如何选择现在吃什么.md

Author: Anduin2017

Diff for: tips/如何选择现在吃什么.md

@@ -24,8 +24,10 @@
 
 解得
 
-* a = floor((N+1)/2)
-* b = ceil((N+1)/2)
+```javascript
+const a = Math.floor((N+1)/2);
+const b = Math.ceil((N+1)/2);
+```
 
 ### 菜的选择